fix(gitflow): pre-commit gitleaks scan falls back to protect --staged on < 8.19

Ubuntu's gitleaks 8.16 package has no git subcommand, so the hook's
"unknown command" exit 1 blocked every commit as a leak. Probe
gitleaks git --help once, fall back to protect --staged; regenerate the
installed hooks. T16c simulates a missing binary with a /usr/bin symlink
farm minus gitleaks instead of a shorter PATH.

githooks/pre-commit

@@ -9,10 +9,15 @@ git rev-parse --verify -q HEAD >/dev/null 2>&1 || exit 0   # root commit — all
 
 # Secret backstop (job7) — any branch, not just protected ones. Non-blocking
 # if gitleaks isn't installed; auto-discovers ./.gitleaks.toml (repo root).
+# gitleaks >= 8.19 scans the index with `git --staged`; older builds (Ubuntu's
+# 8.16 package) only know `protect --staged`, and `git` exits 1 there as an
+# unknown command — which would block every commit. Probe the subcommand first.
 if command -v gitleaks >/dev/null 2>&1; then
-  if ! gitleaks git --staged --no-banner >/dev/null 2>&1; then
+  gl_sub=git
+  gitleaks git --help >/dev/null 2>&1 || gl_sub=protect
+  if ! gitleaks "$gl_sub" --staged --no-banner >/dev/null 2>&1; then
     echo "gitflow pre-commit: BLOCKED — gitleaks found a secret in staged changes." >&2
-    echo "  Details: gitleaks git --staged --no-banner" >&2
+    echo "  Details: gitleaks $gl_sub --staged --no-banner" >&2
     echo "  Genuine false-positive? add an allowlist rule to .gitleaks.toml — never bypass with --no-verify." >&2
     exit 1
   fi